fix: bump k8s manifests branch version (#329)

This PR bumps `k8s-manifests-branch` version. It increases requests rate
limit for GitHub api. Related PR
splunk/ta-automation-k8s-manifests#103
Tested here:
https://github.com/splunk/splunk-add-on-for-amazon-web-services/actions/runs/10697833642/job/29656542503

.github/workflows/reusable-build-test-release.yml

@@ -33,7 +33,7 @@ on:
         required: false
         description: "branch for k8s manifests to run the tests on"
         type: string
-        default: "v3.0.5"
+        default: "v3.0.6"
       scripted-inputs-os-list:
         required: false
         description: "list of OS used for scripted input tests"